1. Technical Field
The present invention relates to an air conditioner having an outdoor unit and a plurality of indoor units, in which the plurality of indoor units can perform a cooling operation or a heating operation at the same time or the heating operation and the cooling operation can be performed in a mixed manner.
2. Background Art
In general, an air conditioner of a fluid pipe and a gas pipe connection type (hereinafter referred to as a “double pipeline type”) is known in which an outdoor unit and a plurality of indoor units are connected through two inter-unit pipelines made up of a fluid pipe and a gas pipe and the plurality of indoor units are made to perform the cooling operation or the heating operation. Also, recently, an air conditioner of a low-pressure gas pipe, a high-pressure gas pipe and a fluid pipe connection type (hereinafter referred to as a “triple pipeline type”) is proposed, in which the outdoor unit and the plurality of indoor units are connected through three inter-unit pipelines made up of a low-pressure gas pipe, a high-pressure gas pipe and a fluid pipe and the plurality of indoor units are made to perform the cooling operation or the heating operation at the same time or the cooling operation and the heating operation are performed in a mixed manner (See JP-B-2804527, for example).
With this type of triple-pipeline type air conditioner, there is a tendency that a plurality of outdoor units are provided in order to reduce the size of each outdoor unit and the number of outdoor units to be operated is adjusted according to an air-conditioning load so as to improve operation efficiency of various air-conditioning operations.
However, the outdoor unit used in the triple-pipeline type air conditioner is provided with a compressor, an outdoor heat exchanger, and an outdoor expansion valve in general and is constituted such that one end of the outdoor heat exchanger is selectively branched and connected to a refrigerant discharge pipe and a refrigerant sucking pipe of the compressor, a high-pressure gas pipe is connected to this refrigerant discharge pipe, a low-pressure gas pipe is connected to the refrigerant sucking pipe, and a fluid pipe is connected to the other end of the outdoor heat exchanger. Thus, configurations of devices connected by pipelines or routing of the pipelines in the triple-pipeline type outdoor unit are more complicated as compared with the double-pipeline type outdoor unit and that raises a development cost and a manufacturing cost, whereby a problem of a high price is caused in the configuration provided with a plurality of triple-pipeline type outdoor units.
On the other hand, to the outdoor unit used in the above-mentioned triple pipeline type air conditioner, the low-pressure gas pipe, the high-pressure gas pipe, and the fluid pipe need to be connected, by which a configuration of a refrigerant circuit is different from that of the double-pipeline type outdoor unit. Thus, the triple-pipeline type outdoor unit has more complicated configuration of devices connected by pipelines or routing of the pipelines as compared with the double-pipeline type outdoor unit, which tends to increase the size of the device configuration. Also, since the triple-pipeline type outdoor unit is independently developed and manufactured separately from the double-pipeline type outdoor unit, there are problems that a development period is extended, a manufacturing line should be newly provided, and a production cost is increased.